DrivenWS6

iTrader: (1)

Hey I was hoping someone could shed a little light on this for me. I have been dealing with an erratic and jumpy speedometer in my 02 Trans Am for a while now. I have searched and searched and studied wiring schematics and still can't seem to find any real cause. It bounces and jumps basically when you are on the gas at all, you can usually let out of it or press the clutch in and it comes back. It started out just jumping every once in a while hen lugging a hill or something in 6th but has gotten worse and does it almost all the time now, its nearly impossible to know how fast you are going. I have replaced the VSS and that did not fix it. I believe the PCM is getting the correct signal because I can set the cruise and it never misses a beat even though the gauge is at zero. The funny thing that I don't quite get and tells me that the cluster is and gauges are ok is that when I connect the scan tool to the data link the gauge instantly works perfect and the scan tool shows perfect signal and speed from the PCM at all times. Does the data link complete a ground of somesort for the cluster? I have checked grounds and they see to be tight and clean. I guess I think that if I can figure what exactly happens when I connect the scan tool that I can track down the issue. Sorry for the long winded post but after all of the searching and reading I have done I had to see if someone had any insight for me. TIA

DrivenWS6

iTrader: (1)

Update:I seem to have fixed it. The ground on the back of the head was a bit loose. I tightened it up and it seems to be working good now.